act up

act of Congress

An authorization that is extremely difficult to obtain, especially in a timely fashion.

act one's age

To behave in a manner appropriate to one's age.

act one's age, not one's shoe size

Synonym of act one's age (“to behave in a mature manner; to avoid being childish”).

act out

To perform something specific.

act the hypocrite

To behave deceitfully or hypocritically; to dissemble.

clean up one's act

To reform; to improve one's habits.

get into the act

To participate in an activity, especially a successful or attractive one.

get one's act together

To become serious, organized, worthwhile, etc.